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Cr-assisted low-temperature densification of(Ti,Zr,Nb,Ta,Mo)C high-entropy carbides with ultrafine grain and enhanced hardness

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Journal of Advanced Ceramics 2024年第6期13卷 780-788页

作者： Yang Liu Jiaji Liang Weiming Guo Shikuan Sun Yu Tian hua-tay lin School of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China State Key Laboratory of High Performance Tools Guangdong University of TechnologyGuangzhou 510006China School of Material Science and Energy Engineering Foshan UniversityFoshan 528000China

While the use of low-melting-point metals as sintering aids for high-entropy carbide(HEC)ceramics has been well established,their existence can compromise hardness due to residual metallic *** study demonstrates an innovative strategy to meet this challenge,where(Ti,Zr,Nb,Ta,Mo)C high-entropy carbide ceramics with ultrafine grains and enhanced hardness are obtained through chromium(Cr)-metal-assisted spark plasma sintering(SPS)at a temperature as low as 1600℃.The results show that the addition of 5 vol%Cr promotes the formation of highly densified single HEC phase ceramics with a high relative density(98.4%)and an ultrafine-grained microstructure(0.17μm).This low-temperature densification mechanism can be attributed to Cr’s solid-solution effect within the matrix and the increased carbon vacancies generated during *** grain size of the(Ti,Zr,Nb,Ta,Mo)C ceramics with 5 vol%Cr metal addition is significantly smaller than that of Cr-free(Ti,Zr,Nb,Ta,Mo)C ceramics sintered at 2000℃(3.03μm)or via traditional low-temperature liquid-phase sintering(1.3–1.5μm).Importantly,the addition of 5 vol%Cr substantially increased the hardness of the ceramics,with a remarkable increase from 23.57 to 28.16 GPa compared to that of the pure(Ti,Zr,Nb,Ta,Mo)C ceramics,owing to the fine-grain strengthening and solid-solution strengthening *** work highlights the uniqueness of Cr metal as a sintering aid in achieving densification and hardness improvements in(Ti,Zr,Nb,Ta,Mo)C ceramics,offering a promising strategy for improving the properties of HEC materials for further development in the near future.

关键词： solid solution sinterability hardness enhancement (Ti,Zr,Nb,Ta,Mo)C high-entropy carbide(HEC)ceramics

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Low-temperature densification of high-entropy(Ti,Zr,Nb,Ta,Mo)C-Co composites with high hardness and high toughness

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Journal of Advanced Ceramics 2022年第5期11卷 805-813页

作者： Si-Chun LUO Wei-Ming GUO Kevin PLUCKNETT hua-tay lin School of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China School of Mechanical and Electronic Engineering Pingxiang UniversityPingxiang 337000China Department of Process Engineering and Applied Science Dalhousie UniversityHalifax B3J1ZICanada

In order to prepare high toughness(Ti,Zr,Nb,Ta,Mo)C ceramics at low temperatures while maintaining high hardness,a liquid-phase sintering process combined with Co-based liquid-phase extrusion strategy was adopted in this *** densification temperature can be lowered to 1350℃,which is much lower than the solid-state sintering temperature(~2000℃)generally employed for high-entropy carbide *** sintered at 1550℃and 30 MPa applied pressure,part of the Co-based liquid-phase was squeezed out of the graphite mold,such that only~3.21 vol%of Co remained in the high-entropy *** to the Co-free solid-state sintered(Ti,Zr,Nb,Ta,Mo)C ceramics,prepared at 2000℃and 35 MPa,the hardness was slightly decreased from 25.06±0.32 to 24.11±0.75 GPa,but the toughness was increased from 2.25±0.22 to 4.07±0.13 MPa·m^(1/2).This work provides a new strategy for low-temperature densification of high-entropy carbides with both high hardness and high toughness.

关键词： high-entropy carbide ceramics liquid-phase sintering microstructure grain size mechanical properties

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Design strategy of phase and microstructure of Si_(3)N_(4) ceramics with simultaneously high hardness and toughness

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Journal of Advanced Ceramics 2023年第1期12卷 122-131页

作者： Shao-Jun TANG Wei-Ming GUO Shi-Kuan SUN hua-tay lin School of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China School of Material Science and Energy Engineering Foshan UniversityFoshan 528000China

Aiming to achieve silicon nitride( Si_(3)N_(4))ceramics with high hardness and high toughness,the relationships among phase composition,microstructure,and mechanical properties of Si_(3)N_(4) ceramics prepared by spark plasma sintering(SPS)at temperatures ranging from 1500 to 1800℃were investigated in this *** stages with different phase and microstructure features were observed and ***α-βphase transformation occurs first,and the development and growth of grains lag *** the first stage,the average grain size remains basically unchanged,and the hardness maintains at a value of~20.18±0.26 GPa,despite theβ- Si_(3)N_(4) phase fraction increases from 7.67 to 57.34 wt%.Subsequently,the equiaxed grains transform into rod-like grains with a high aspect ratio via the reprecipitation process,resulting in a significant increase in the fracture toughness from 3.36±0.62 to 7.11±0.15 MPa·m^(1/2).In the second stage of sintering process,the fraction ofβ- Si_(3)N_(4) phase increases to 100.00 wt%,and the grain growth also rapidly ***,the fracture toughness increases slightly to 7.61±0.42 MPa·m^(1/2),but the hardness reduces to 16.80±0.20 *** current results demonstrate that the phase contents ofβ- Si_(3)N_(4) and the microstructure shall be carefully tailored to achieve high-performance Si_(3)N_(4) ceramics. Si_(3)N_(4) ceramics with a finegrained bimodal microstructure,consisting of the mainα-andβ-phases,can exhibit the optimized combination of hardness and toughness.

关键词： silicon nitride(Si_(3)N_(4)) phase composition microstructure hardness toughness

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Fabrication and modelling of Si_(3)N_(4)ceramics with radial grain alignment generated through centripetal sinter-forging

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Journal of Materials Science & Technology 2022年第31期126卷 1-14页

作者： Da-Wang Tan Zhen-Yong Lao Wei-Ming Guo Akira Kondo Takahiro Kozawa Makio Naito Kevin Plucknett hua-tay lin Department of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China Joining and Welding Research Institute Osaka University11-1 MihogaokaIbarakiOsaka 567-0047Japan Department of Mechanical Engineering Dalhousie UniversityHalifaxNova Scotia B3H 4R2Canada

Silicon nitride(Si_(3)N_(4))based ceramics are one of the most attractive advanced engineering materials,which have been widely used under high-speed rotational operation or for mechanical contacts across a curved *** the present study,rotationally symmetric texturing of Si_(3)N_(4),with radial grain align-ment,was obtained by centripetal sinter-forging(CSF)of a partially sintered *** average values of the included angles between the c-axis of the local Si_(3)N_(4)grain and radial direction were approxi-mately 16.4°and 11.0°,on the section plane perpendicular to the pressing direction,and parallel to both the pressing and radial directions,*** compressive strain in the pressing direction forced the ceramic body to flow towards the central axis,resulting in compressive strain in the tangential di-rection and tensile strain in the radial direction.A fundamental physical model was created to simulate the grain rotation during the 3-dimentional strain reorientation,which revealed the rod-like grain would preferentially rotate toward the center of the sample under the CSF *** addition,due to the fric-tion between the sample surface and the pressing punch,the increased shear strain could enhance the Si_(3)N_(4)grain ***,ceramics with rod-like grains perpendicular to the curved side sur-face could be anticipated by applying the centripetal forming concept in a controlled manner.

关键词： Si_(3)N_(4)ceramic Texture Radial grain alignment Modeling CSF

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Optimal preparation of high-entropy boride-silicon carbide ceramics

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Journal of Advanced Ceramics 2021年第1期10卷 173-180页

作者： Yan ZHANG Shi-Kuan SUN Wei-Ming GUO Liang XU Wei ZHANG hua-tay lin School of Electron-mechanical Engineering Guangdong University of TechnologyGuangzhou 510006China Department of Materials Science and Engineering University of SheffieldSheffield SI 3JDUK

High-entropy boride-silicon carbide(HEB-SiC)ceramics were fabricated using boridebased powders prepared from borothermal and boro/carbothermal reduction *** effects of processing routes(borothermal reduction and boro/carbothermal reduction)on the HEB powders were ***-SiC ceramics with>98%theoretical density were prepared by spark plasma sintering at 2000℃.It was demonstrated that the addition of SiC led to slight coarsening of the *** HEB-SiC ceramics prepared from boro/carbothermal reduction powders showed a fine-grained microstructure and higher Vickers9 hardness but lower fracture toughness value as compared with the same composition prepared from borothermal reduction *** results indicated that the selection of the powder processing method and the addition of SiC phase could contribute to the optimal preparation of high-entropy boride-based ceramics.

关键词： high-entropy boride-silicon ceramics borothermal reduction boro/carbothermal reduction microstructure mechanical properties

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Textured and toughened high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C-SiCw ceramics

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Journal of Materials Science & Technology 2021年第35期94卷 99-103页

作者： Si-Chun Luo Wei-Ming Guo Yu-Zhang Zhou Kevin Plucknett hua-tay lin School of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China College of Mechanical and Electronic Engineering Pingxiang UniversityPingxiang337000China Department of Process Engineering and Applied Science Dalhousie UniversityHalifax B3J 1Z1Canada

High-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C ceramics,with different contents(0,5,10,and 20 vol.%)of Si C whiskers(SiCw),were fabricated by spark plasma sintering using raw powders synthesized via carbothermal *** application of a uniaxial compaction force led to texture development of the SiCw within the(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C *** toughness increased with the increase in SiCw content,while Vickers hardness remains almost *** toughness of(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C-20 vol.%SiCw ceramics reached 4.3±0.3 MPa m^(1/2),which was approximately 43%higher than that of the monolithic(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C ceramic(3.0±0.2 MPa m1/2).The main toughening mechanisms were attributed to crack deflection,whisker debonding,and whisker pullout.

关键词： High-entropy carbide ceramics Silican carbide whiskers Microstructure Mechanical properties Toughening mechanism

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Elimination of methicillin‑resistant Staphylococcus aureus biofilms on titanium implants via photothermally‑triggered nitric oxide and immunotherapy for enhanced osseointegration

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Military Medical Research 2024年第2期11卷 157-179页

作者： Yong‑lin Yu Jun‑Jie Wu Chuan‑Chuan lin Xian Qin Franklin R.tay Li Miao Bai‑Long Tao Yang Jiao Department of Pathology Affiliated Hospital of Zunyi Medical UniversityZunyi 563003GuizhouChina Laboratory Research Center the First Affiliated Hospital of Chongqing Medical UniversityChongqing 400016China Department of Blood Transfusion Laboratory of Radiation Biologythe Second Affiliated HospitalArmy Military Medical UniversityChongqing 400037China Department of Reproductive Endocrinology Chongqing Health Center for Women and ChildrenChongqing 401147China The Graduate School Augusta UniversityAugustaGA 30912USA Department of Stomatology the Seventh Medical Center of PLA General HospitalBeijing 100700China

Background:Treatment of methicillin-resistant Staphylococcus aureus(MRSA)biofilm infections in implant placement surgery is limited by the lack of antimicrobial activity of titanium(Ti)*** is a need to explore more effective approaches for the treatment of MRSA biofilm ***:Herein,an interfacial functionalization strategy is proposed by the integration of mesoporous polydopamine nanoparticles(PDA),nitric oxide(NO)release donor sodium nitroprusside(SNP)and osteogenic growth peptide(OGP)onto Ti implants,denoted as Ti-PDA@*** physical and chemical properties of Ti-PDA@SNP-OGP were assessed by scanning electron microscopy,X-ray photoelectron spectroscope,water contact angle,photothermal property and NO release *** synergistic antibacterial effect and elimination of the MRSA biofilms were evaluated by 2′,7′-dichlorofluorescein diacetate probe,1-N-phenylnaphthylamine assay,adenosine triphosphate intensity,O-nitrophenyl-β-D-galactopyranoside hydrolysis activity,bicinchoninic acid *** staining,assays for alkaline phosphatase activity,collagen secretion and extracellular matrix mineralization,quantitative real‑time reverse transcription‑polymerase chain reaction,and enzyme-linked immunosorbent assay(ELISA)were used to evaluate the inflammatory response and osteogenic ability in bone marrow stromal cells(MSCs),RAW264.7 cells and their co-culture *** staining,ELISA,micro-CT,hematoxylin and eosin,Masson's trichrome and immunohistochemistry staining were used to evaluate the eradication of MRSA biofilms,inhibition of inflammatory response,and promotion of osseointegration of Ti-PDA@SNP-OGP in ***:Ti-PDA@SNP-OGP displayed a synergistic photothermal and NO-dependent antibacterial effect against MRSA following near-infrared light(NIR)irradiation,and effectively eliminated the formed MRSA biofilms by inducing reactive oxygen species(ROS)-mediated oxidative stress,destroying bacterial membrane integrity and

关键词： Polydopamine nanoparticles Methicillin-resistant Staphylococcus aureus Nitric oxide Osseointegration Osteo-immunomodulation Photothermal effect Titanium implants

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Effect of Mo and cold forging deformation on strength and ductility of cobalt-based alloy L605

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Journal of Iron and Steel Research(International) 2024年第7期31卷 1811-1823页

作者： Zhong-lin Wang Zhi-hua Gong Quan Li Han-sheng Bao School of Materials and Metallurgy Inner Mongolia University of Science and TechnologyBaotou 014017Inner MongoliaChina Institute of Special Steels Central Iron and Steel Research Institute Co.Ltd.Beijing 100081China

Mo element was added to cobalt-based alloy L605,and cold forging deformation was *** effects of the addition and cold forging deformation on the microstructure and mechanical properties of the alloy were studied by thermodynamic calculation,electron backscatter diffraction,transmission electron microscopy,and X-ray *** stacking fault energy(SFE)of the alloy decreased after the addition,and the formation of stacking faults and intersections were promoted to improve the strength and *** tensile strength of the alloy with Mo increased from 1190 to 1702 MPa after 24%cold deformation,producing significant work *** strengthening mechanism is strain-induced martensitic transformation(SIMT)and deformation *** alloy,combined with Mo and after 24%deformation,had both high strength and ductility in comparison with the original cobalt-based alloy *** is attributed to the lower SFE which caused the increase in stacking fault *** the tensile process,theε-hcp phase was easily generated at the stacking fault to reduce the stress concentration and increase the *** SIMT by adjusting the density of stacking faults can improve the mechanical properties of cobalt-based ***ε-hcp phase,the interaction between deformation twins and dislocations,and the interaction between e-hcp phases during cold forging deformation caused local stress concentration,lowering ductility and toughness.

关键词： Cobalt-based alloy-Stacking fault energy Strain-induced martensitic transformation Deformation twin Cold forging deformation

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Cr-catalyzed allylic C(sp^(3))–H addition to aldehydes enabled by photoinduced ligand-to-metal charge transfer

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Science China Chemistry 2024年第5期67卷 1589-1595页

作者： Xianrong Zeng Feng-hua Zhang Runchen Lai Xiaoyu lin Zhaobin Wang Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province Department of ChemistrySchool of Science and Research Center for Industries of the FutureWestlake UniversityHangzhou 310030China Institute of Natural Sciences Westlake Institute for Advanced StudyHangzhou 310024China Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province Instrumentation and Service Center for Molecular SciencesWestlake UniversityHangzhou 310024China

Photoinduced ligand-to-metal charge transfer(LMCT) has emerged as an effective strategy for synthesizing organic molecules in a sustainable manner. However, the majority of existing reports on selective C(sp^(3))–H bond functionalization via photoinduced LMCT focus on the use of late transition metals or rare-earth metals for radical additions or cross-couplings. In contrast, the utilization of photoinduced LMCT with 3d early transition metals poses a significant challenge. Herein, we describe an unprecedented approach to allylic C(sp^(3))–H addition to aldehydes, employing chromium(Cr) complexes as catalysts through visible-light-induced LMCT. By investigating the reaction pathway through various mechanistic studies, including radical trapping, kinetic isotope effect(KIE) analysis, and transient absorption spectroscopy, valuable insights have been gained. The proposed mechanism suggests the intermediacy of bromine radicals through homolysis of the Cr–Br bond. Notably, this protocol expands our understanding of the photochemical properties of earth-abundant Cr complexes.

关键词： Cr catalysis photoinduced ligand-to-metal charge transfer hydrogen-atom transfer carbonyl addition

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Evaluation of suitability,adaptability,and reserve potential of construction land on the Qinghai-Tibet Plateau

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Journal of Geographical Sciences 2024年第1期34卷 41-61页

作者： YANG hua XU Yong ZHOU Kan WANG Lijia XU lin Key Laboratory of Regional Sustainable Development Modeling Institute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Construction land is the leading carrier of human activities such as production and *** the construction land suitability(CLS)on the Qinghai-Tibet Plateau(QTP)holds significant implications for harmonizing the relationship between ecological protection and human activity and promoting population and industry layout ***,no relevant studies provide a complete CLS assessment of the *** this study,we developed a model-based CLS evaluation framework coupling of pattern and process to calculate the global CLS on the QTP based on a previously developed CLS evaluation ***,using the land-use data of 1990,2000,2010,and 2020,we examined the adaptability of existing construction land(ECL)to the CLS assessment result through the adaptability index and vertical gradient index and further analyzed the limitations of maladaptive construction ***,we calculated the potential area of reserve suitable construction *** article includes four conclusions:(1)The highly suitable,suitable,moderately suitable,marginally suitable,and unsuitable CLS classes cover areas of 0.33×10^(4)km^(2),10.42×10^(4)km^(2),18.06×10^(4)km^(2),24.12×10^(4)km^(2),and 205.29×10^(4)km^(2),*** approximately 11%of the study area on the QTP is suitable for large-scale permanent construction land,and approximately 79.50%of the area is unsuitable under current economic and technological conditions.(2)The ECL adaptability index is 85.16%,85.93%,85.18%,and 78.01%during 1990–2020,respectively,with an average adaptability index exceeding 80%on the *** ECL distribution generally conforms to construction land suitable space characteristics but with a significant spatial difference.(3)From 1990 to 2020,the maladaptive ECL was dominated by rural settlement land,transport land,and special land,with a rapidly increasing proportion of urban and other construction *** maladaptive ECL is constrained by both elevation and slope in the southern Qinghai Pla

关键词： land resource construction land suitability existing construction land adaptability human activity Qinghai-Tibet Plateau

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